A magnetic head suspension is required to have such a high resonance frequency in torsion mode as to allow a magnetic head to be moved at high speed in seeking direction and positioned at a target track with a high accuracy.
To increase the resonance frequency in torsion mode, it is effective to improve torsion rigidity of a load beam. However, only the employment of a thicker load beam is insufficient. That is, thickening of a load beam, which achieves increased torsion rigidity, also results in increased weight, which makes it hard to sufficiently increase the resonance frequency.
The load beam having such an increased weight also invites deterioration in impact load carrying capacity of the suspension. That is, as the weight of the load beam is increased, the maximum rate of acceleration of the load beam in a direction away from a disk surface is lowered. As a result, it is highly likely to invite damages to the disk surface due to bouncing of the load beam.
In consideration of the above matters, the specification of the U.S. Pat. No. 3,931,641 describes a load beam which was designed in attempt to simultaneously achieve improvements in resonance frequency and impact load carrying capacity by reducing the weight of the load beam by eliminating a portion of the load beam with leaving the portion necessary for a required rigidity. More specifically, the specification of the above cited U.S. patent describes a load beam having a triangular shape in plan and a hollow center. This load beam is welded to a plate material formed by an integral arrangement of a flexure and a load-bent portion (see FIG. 8). The same idea regarding the arrangement of the above cited U.S. patent is also described in Japanese Patent Application Laid-open Nos. Hei-10-031873, 2001-143422 and 2001-155458.
A load beam described in each of those cited references (see FIG. 8) is merely formed into a triangular shape in plan, and therefore hard to reduce the moment of inertia around the longitudinal axis although it can achieve an improved resonance frequency in sway mode. As a result, it is difficult to sufficiently improve the resonance frequency in torsion mode.
The present invention has been conceived in consideration of the above problems. It is an object of the present invention to provide a magnetic head suspension that is capable of improving the rigidity of the load beam while limiting increase of the weight, and increasing the resonance frequency in torsion mode.